LONDON — Facial recognition technology being considered for London's 2012 Games is getting a workout in the wake of Britain's riots, a senior police chief told The Associated Press on Thursday, with officers feeding photographs of suspects through Scotland Yard's newly updated face-matching program.

Chief Constable Andy Trotter, who is helping London police in the wake of the riots, said the department's sophisticated software was being used to help find those suspected of being involved in the worst unrest London has seen in a generation.

But he cautioned that facial recognition makes up only a fraction of the police force's efforts, saying tips have mostly come from traditional sources, such as still images captured from closed circuit cameras, pictures gathered by officers, footage shot by police helicopters or images snapped by members of the public.

"There's a mass of evidence out there," Trotter said in a telephone interview. "The public are so enraged that people who wouldn't normally come forward are helping us — especially when they see their neighbors are coming back with brand new TVs."

The facial-recognition technology used by police treats the human face like a grid, measuring the distance between a person's nose, eyes, lips and other features. It has recently been upgraded, according to an article published last year in Scotland Yard's bimonthly magazine, "The Job."

The March 2010 article said that the new program has been shown to work far better than older versions of the technology, with one expert quoted as saying that it had shown promise in identifying people from high-quality, face-on shots taken off of surveillance photographs, mobile phones, passports or the Internet.

A law enforcement official told the AP that to use the technology "you have to have a good picture of a suspect and it is only useful if you have something to match it against. In other words, the suspect already has to have a previous criminal record."

He spoke on condition of anonymity because he was not authorized to discuss ongoing investigations.

A press officer with Scotland Yard — who also spoke anonymously, in line with force policy — confirmed that facial recognition technology was at the police's disposal, although he gave few other details. He said that generally the technology would only be used to help identify those suspected of serious crimes, such as assault, and that in most cases disseminating photographs to the general public remains a far cheaper and more effective way of finding suspects.

To that end the police have released two dozen photos and videos to the picture-sharing website Flickr, where they've already gathered more than 400,000 hits. Some of those photographs have also been published by Britain's brash tabloid press. The Sun recently plastered them across its front page, along with a headline urging readers to report looters to the police.

Nigel Howard
/
AP

Chief Superintendent Simon Ovens, left, commander of the Westminster Burglary Squad, and another officer arrest a suspect in a raid by police in an attempt to recover property stolen during the civil disturbances.

The photographs on Flickr are mainly grainy images pulled from cameras, which may not be of much use to face-matching software. But detectives are already scanning the Web for pictures of high-quality photographs of rioters' faces, according to photojournalist Guilherme Zauith, who witnessed some of the disturbances in London and later posted images of clashes to the Internet.

Zauith said he was recently contacted by a London detective "saying that they saw my photos online and if I could send it to them to help to identify the people."

"They were looking for all kind of photographs showing faces," he said.

Such programs have been of increasing interest to authorities as well. A person with the Olympic planning committee, speaking to the AP on condition of anonymity because of the sensitivity of security preparations, said that facial recognition software was being considered for use as a security measure during the Olympic Games.

Meanwhile, detectives are employing a host of other tactics to take aim at the rioters. Police departments across the country have made arrests linked to riot threats and boasts posted to social networking sites.

Trotter said that while investigations had been helped by looters "who publicize their actions on things like Facebook," a lot of arrests have come the old-fashioned way, through officers simply spotting suspects they'd seen before.

"It's not just the face that is recognizable," Trotter said. "It's been in the way they walk, or the clothes they're wearing or even tattoos."

Video: London police crack down on rioters

Transcript of: London police crack down on rioters

BRIAN WILLIAMS, anchor:Now we turn to
London
. The streets are calm tonight. Some of the
police officers
who've been dispatched to keep the peace spent today raiding homes, rounding up suspects that have been identified from those four straight nights of violence, riots, fires, looting. Meanwhile Prime Minister
David Cameron
said today he'd look here to the
United States
for help in preventing a repeat. He specifically mentioned a familiar name in the police business,
William Bratton
, the former chief of police here in
New York
and
LA
and
Boston
, as someone who might offer some solutions.